Figure
A. First total synthesis of (±)-heliannuol A. B. First total synthesis of (±)-heliannane.
All the synthesis mentioned end up with racemic mixtures. In spite of the high importance of getting enantiopure compounds, the first report of an enantioselective total synthesis of heliannuols A and D have not been published until recently.47 The key point of the synthetic strategy was to get access to the enantiopure epoxide 35. Base-catalized intramolecular cyclization led to the desired heliannuols A and D in enantiopure forms.
MCPBA
Na2HPO4 DCM OMe 26
MCPBA
Na2HPO4 DCM OMe 26
OMe 27
- KOH, DMSO, 70-100°C
- NaSEt, DMF, ref.
- KOH, DMSO, 70-100°C
- NaSEt, DMF, ref.
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